This invention relates to a deciphering device for utilization within a data processing environment and, more particularly, to a deciphering device for decoding ciphered information stored in a memory system, insuring complete security and privacy of the information stored within the memory system of the data processing environment.
Intellectual properties such as software, firmware, data bases or any other form of collected information may be recorded using a wide variety of memory technologies. Certain of these memory technologies are intended for direct access by a computer system or processing element. Such memory technologies include ROM, RAM, CAM, writeable control store, etc. When information is stored in a memory system of a data processing environment using these technologies, it may be directly available to unauthorized access. ROM devices are particularly vulnerable due to their easy removability. With the increasing use of telecommunications in computer system networks, the very long cable connection between terminals or I/O devices and control units and the easy removability of storage medium of the memory system, there is an increasing concern over the interception or alteration of information because physical protection cannot always be guaranteed. Cryptography has been recognized as one type of mechanism for achieving data security and privacy in that it protects the data itself rather than the medium of storing or transmitting the information.
Various systems have been developed for enciphering/deciphering messages to maintain the security and privacy of information stored in the memory elements or storage medium within the data processing environment and for the communication of the information between data processing systems. One such enciphering system is a block cipher system, which is a substitution technique in which an entire block of information is enciphered in accordance with a predetermined cipher key. The resulting substituted information is unintelligible cipher text which cannot be understood without knowledge of the cipher key. Another cipher system relates to a product cipher which combines linear and nonlinear transformations of a clear text message with the transformations being a function of a cipher key. Still another cipher system is directed to a product cipher system in which the block of clear text is processed on a segment basis in which each segment is serially transformed in accordance with a portion of the cipher key.
In many of the prior art systems knowledge of the cipher key enables the data to be deciphered relatively easily. Therefore, there exists a need for an improved cipher/decipher system in which knowledge of the cipher key and/or knowledge of the combining function of the key with the ciphered text is insufficient to decipher the stored information, hence, providing additional security for the information stored in the memory element or storage medium.